Antenna mounting questions

I'm a truck driver and I just got a brand new Sirius Edge radio for my 2012 Volvo. I got the bracketed mirror mounted antenna after the smaller magnetic mounted antenna that came with the radio was found to be lacking. The new antenna is better, but sometimes the truck's superstructure still blocks the signal. And we're talking flat desert I10 going through Arizona and New Mexico. Where and how is the best place to mount an antenna on a big truck. Also, is it possible to install two antennas (on on either side of the truck) and then run them to the radio through a splitter? I can only see this problem getting worse in mountainous terrain if I don't fix the problem. I could really use some tips.

Get that sucker as high as possible on your rig. I'd give that same advice to anyone driving anything.

I took a Winnebago from Boston to Daytona and putting the antenna on the dash worked well most of the time but about half way down we said, screw it, and slapped that thing right on top of the roof and it was clear sailing the rest of the way down and back.

I'd find a way to run the little original antenna out of your cab and up to the highest point possible. You probably wont even see it sitting up there and you'll have perfect reception with a 360 degree clear view of the sky.

Does your truck have a wind deflector and a skylight up top of the sleeper? Can you post a picture of it (or a link to your model)? You might be able to put the antenna in your skylight and mount it inside your truck. It will have no problem through the glass. I mounted mine inside my jeep and it picks up reception through the softtop.